Muscle

Question 1

tropomyosin

Answer 1

blocks binding sites on actin filaments which prevents myosin cross-bridge binding and prevents contraction in muscle as a result

Question 2

troponin

Answer 2

blocks tropomyosin in place in the actin binding site
has a high affinity for Ca2+so when calcium levels rise they bind to troponin and move it and therefore move tropomyosin too unblocking the binding site

Question 3

which topic do you remember the sarcolemma from?

Answer 3

autonomic physiology and Neuromuscular junction!!!

it’s the membrane on post synaptic terminal at NMJ

Question 4

the sarcolemma has ___ that that penetrate into interior of muscle

Answer 4

it has transverse tubules that penetrate into the centre of skeletal and cardiac muscle

Question 5

what do you have in cardiac and skeletal muscle

Answer 5

blood supply
mitochondria
sarcoplasmic reticulum

Question 6

what is the function of the sarcoplasmic reticulum

Answer 6

calcium storage (easy access for the muscle)

Question 7

characteristics of the transverse tubules

Answer 7

they protect depolarisation

are specific

Question 8

release of Ca2+ from sarcoplasmic reticulum

Answer 8

depolarisation (caused by neurotransmitter binding on post-synaptic terminal receptors) flows down the transverse tubules

receptors on the S.R detect this depolarisation and it causes voltage gated Ca2+ channels (these aren’t on tubule side) to open allowing Ca2+ to pass through into the interior of muscle

as calcium levels rise it binds to troponin which pulls tropomysin away from actin binding site unblocking it. Myosin is now able to bind and MUSCLE CONTRACTION CAN NOW OCCUR

Question 9

how and why is calcium taken back up

Answer 9

it’s taken back up into S.R by active transport- active calcium pumps keeps pumping it back into storage
re-blocking actin binding site. Ends contraction and muscle fibre relaxes

Question 10

what happens when Ca2+ levels are high for too long?

Answer 10

muscle fatigue

and tension crashes once it’s at maximum

Question 11

what do contraction and relaxation rely on

Answer 11

ATP

Question 12

isotonic twitch

Answer 12

2 types contracting- shortening length, extending- lengthening
a constant tension but shortening or lengthening of muscle at same time
ie bicep curls

Question 13

isometric twitch

Answer 13

holding a pose or fixed position
has same tension/ contraction is held
e.g like holding a glass of water in a position and someone filling it- you’re increasing the load but force exerted by muscle is the same

Question 14

what is tetanus

Answer 14

when multiple twitches/small contractions that are from separate motor units but happen close together summate and feel like one big contraction

Question 15

during vigorous muscle contraction what happens when maximum tension is reached

Answer 15

all the actin binding sites are exposed so myosin goes through cycle until it can’t increase muscle force anymore (no matter increasing calcium or A.Ps)

because there is a finite ATP supply you can’t maintain vigorous excersise- the cycle can’t be completed
Need ATP and O2 for muscle contraction and relaxation

Question 16

what is the only thing you can measure to create a grade of force? and what is measured by this

Answer 16

frequency
Action potentials are one intensity (non-decremental, all or none)
they can be measured

Question 17

what are the two different types of fibres and what do they do differently?

Answer 17

oxidative
glycolytic
they produce ATP in different ways

Question 18

oxidative fibres

Answer 18

they carry out oxidative phsophorylation (ATP SYNTHASE- ETC)
have many mitochondria in their fibres
have fast and slow types
slow are the most resistant to fatigue

Question 19

glycolytic

Answer 19

split glucose for energy

fast glycolytic- fatigue quickly- have few mitochondria

Question 20

what is recruitment

Answer 20

activating more motor units (muscle and motor neuron) to accommodate an increase in load on a muscle

Question 21

which fibres would be activated first

Answer 21

slow oxidative as most resistant to fatigue

Question 22

difference of SMOOTH muscle to cardiac and skeletal

Answer 22

innervated by autonomic nervous system not somatic
actin and myosin are arranged diagonally across cells not straight
different cross bridge cycle but still relies on Ca2+

Question 23

Smooth muscle cross-bridge cycle

Answer 23

increase in calcium levels
calcium released from sarcoplasmic reticulum
it then binds to calmodulin protein activating it

calmodulin binds to myosin light chain kinase which goes on to phosphorylate myosin cross-bridges with ATP
the phosphorylated cross-bridge binds to actin filaments and CONTRACTION occurs

Question 24

how does smooth muscle relax

Answer 24

dephosphorylation of cross bridges by myosin light chain phosphatase

Question 25

persistant stimulation and increase of Ca2+ in SMOOTH muscle

Answer 25

you can dephosphorylate cross bridges are whilst still bound to actin then there is a decrease in ATP and this slows the cross bridge cycle which means you can maintain tension for a long time with low ATP consumption USEFUL in blood vessel walls that need to stay open fr long periods

Question 26

sources of cytosolic Ca2+ for smooth muscle contraction

Answer 26

there is less sarcoplasmic reticulum in smooth muscle than skeletal extracellular Ca2+ comes through voltage gates channels too Ca2+ is removed from cytosol by pumping it back into S.R and out of the cell by Ca2+ ATPases SLOWER PROCESS- more going on

Question 27

smooth muscle single unit

Answer 27

GIT, uterus, small blood vessel signals travel between cells linked by gap junctions contract synchronously stretch evokes contraction

Question 28

smooth muscle multi unit

Answer 28

airways, large arteries, hairs few or no gap junctions richly innervated by autonomic nervous system- need more as multiunit is less responsive don't respond to stretch

Question 29

what factors affect contractile activity in smooth muscle

Answer 29

hormones - oxytocin- lactation in breast muscle stretch spontaneous electrical activity in muscle membranes- pacemaker

Question 30

autorhythmicity

Answer 30

creating own rhythm- cardiac muscle cells

Question 31

intercalated discs

Answer 31

join cardiac muscle cells together gap junction allow for cell-cell communication

Question 32

what is the cardiac action potential

Answer 32

it is a brief change in voltage (membrane potential) across the cell membrane of heart cells

Question 33

what is the pacemaker potential

Answer 33

the slow, positive increase in voltage across the cell's membrane that occurs between the end of one action potential and the beginning of the next action potential so recovers it